Photoinduced electron transfer across the polymer-capped CsPbBr₃ interface in a polar medium

In-situ polymer capping of cesium lead bromide (CsPbBr₃) nanocrystals with polymethyl acrylate is an effective approach to improve the colloidal stability in the polar medium and thus extends their use in photocatalysis. The photoinduced electron transfer properties of polymethyl acrylate (PMA)-capped CsPbBr₃ nanocrystals have been probed using surface-bound viologen molecules with different alkyl chains as electron acceptors. The apparent association constant (K_app) obtained for the binding of viologen molecules with PMA-capped CsPbBr₃ was 2.3 × 10⁷ M^-1, which is an order of magnitude greater than that obtained with oleic acid/oleylamine-capped CsPbBr₃. Although the length of the alkyl chain of the viologen molecule did not show any impact on the electron transfer rate constant, it influenced the charge separation efficiency and net electron transfer quantum yield. Viologen moieties with a shorter alkyl chain length exhibited a charge separation efficiency of 72% compared with 50% for the longer chain alkyl chain length viologens. Implications of polymer-capped CsPbBr₃ perovskite nanocrystals for carrying out photocatalytic reduction in the polar medium are discussed.